Parallelized writing of servo RRO/ZAP fields

ABSTRACT

An apparatus may include a first and second servo channels configured to output first and second position information to first and second writers, respectively, via a shared write path such that the first and second writers write first and second position information to first and second magnetic recording medium surfaces, respectively. In addition, the apparatus may include a controller configured to control the shared write path such that write access is changed between the first servo channel and second servo channel a plurality of times during a revolution of the first magnetic recording medium surface and second magnetic recording medium surface.

SUMMARY

In certain embodiments, an apparatus may include a first servo channelconfigured to output first position information to a first writer via ashared write path such that the first writer writes the first positioninformation to a first magnetic recording medium surface and a secondservo channel configured to output second position information to asecond writer via the shared write path such that the second writerwrites the second position information to a second magnetic recordingmedium surface. In addition, the apparatus may include a controllerconfigured to control the shared write path such that write access ischanged between the first servo channel and second servo channel aplurality of times during a revolution of the first magnetic recordingmedium surface and second magnetic recording medium surface.

In certain embodiments, a system may include a first servo channelconfigured to output first position information to a first writer suchthat the first writer writes the first position information to a firstmagnetic recording medium surface of a hard disk drive and a secondservo channel configured to output second position information to asecond writer such that the second writer writes the second positioninformation to a second magnetic recording medium surface of the harddisk drive. The first servo channel may be configured to output firstposition information to the first writer such that the first positioninformation is written to a first location and a second location,separate from the first location, during a particular revolution and thesecond servo channel may be configured to output second positioninformation to the second writer such that the second positioninformation is written to a third location during the particularrevolution. In some embodiments, the third location is between the firstlocation and second location.

In certain embodiments, a method may include, during a revolution of ahard disk assembly of a multi-sensor magnetic recording (MSMR) harddrive, reading, by a first reader of the MSMR hard drive, from a firstmagnetic recording medium surface to generate a first read signal,determining, by a first servo channel of the MSMR hard drive, a firstwrite position at which to write first position information based atleast in part on the first read signal, requesting, from a controller ofthe MSMR hard drive, by the first servo channel, write access to ashared write path based on the determined first write position,receiving, by the first servo channel, a first assignment of writeaccess, outputting, by the first servo channel, the first positioninformation to a first writer via the shared write path, and returning,by the first servo channel, write access to the controller when theoutput of the first position information is complete. During the samerevolution, the method may further include reading, by a second readerof the MSMR hard drive, from a second magnetic recording medium surfaceto generate a second read signal, determining, by a second servo channelof the MSMR hard drive, a second write position at which to write secondposition information based at least in part on the second read signal,requesting, from the controller of the MSMR hard drive, by the secondservo channel, write access to the shared write path based on thedetermined second write position, receiving, by the second servochannel, a second assignment of write access, outputting, by the secondservo channel, the second position information to a second writer viathe shared write path, and returning, by the second servo channel, writeaccess to the controller when the output of the second positioninformation is complete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a multi-sensor magnetic recording (MSMR)system architecture which may include functionality to write positioninformation such as servo fields, RRO/ZAP fields or other formattinginformation to a plurality of storage surfaces in parallel, inaccordance with certain embodiments of the present disclosure;

A FIG. 2 illustrates a block diagram of a surface of an example magneticstorage mediums of the multi-sensor magnetic recording (MSMR) systemarchitecture, in accordance with certain embodiments of the presentdisclosure;

FIG. 3 illustrates a block diagram of a block diagram of a multi-sensormagnetic recording (MSMR) system architecture which may includefunctionality to write position information such as servo fields,RRO/ZAP fields or other formatting information to a plurality of storagesurfaces in parallel, in accordance with certain embodiments of thepresent disclosure;

FIG. 4 is a flowchart of a method that may control parallelized writingof RRO/ZAP fields to multiple storage surfaces, in accordance withcertain embodiments of the present disclosure;

FIG. 5 is a block diagram of a system including a multi-sensor magneticrecording (MSMR) system architecture which may include functionality towrite position information such as servo fields, RRO/ZAP fields or otherformatting information to a plurality of storage surfaces in parallel,in accordance with certain embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description of the embodiments, reference ismade to the accompanying drawings which form a part hereof, and in whichare shown by way of illustrations. It is to be understood that featuresof the various described embodiments may be combined, other embodimentsmay be utilized, and structural changes may be made without departingfrom the scope of the present disclosure. It is also to be understoodthat features of the various embodiments and examples herein can becombined, exchanged, or removed without departing from the scope of thepresent disclosure.

In accordance with various embodiments, the methods and functionsdescribed herein may be implemented as one or more software programsrunning on a computer processor or controller. In accordance withanother embodiment, the methods and functions described herein may beimplemented as one or more software programs running on a computingdevice, such as a personal computer that is using a disc drive.Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays, andother hardware devices can likewise be constructed to implement themethods and functions described herein. Further, the methods describedherein may be implemented as a computer readable storage medium ordevice including instructions that when executed cause a processor toperform the methods.

The present disclosure generally relates to multi-sensor magneticrecording (MSMR) systems, and in some embodiments, the presentdisclosure may relate to MSMR hard drives that may include functionalityto write position information such as servo fields, RRO/ZAP fields orother formatting information to a plurality of storage surfaces inparallel. MSMR systems according to this disclosure may further performthe writing of the position information to the plurality of storagesurfaces in parallel using the plurality of read paths and single writepath of an MSMR architecture. In some embodiments, the MSMR systems maybe configured to coordinate write access between the servo channels thatmay control the writers that may write to corresponding surfaces of theplurality of storage surfaces. Some MSMR systems according to thisdisclosure may also allow for the parallelized writing to the multiplesurfaces to be performed using separate clock domains.

An example of such a system is discussed below with regard to FIG. 1.

Referring to FIG. 1, a block diagram of a multi-sensor magneticrecording (MSMR) system architecture which may include functionality towrite position information such as servo fields, RRO/ZAP fields or otherformatting information to a plurality of storage surfaces in parallel isshown and is generally designated 100. More particularly, FIG. 1 mayillustrate an example embodiment of a MSMR hard drive that may includefunctionality to write position information such as servo fields,RRO/ZAP fields or other formatting information to a plurality of storagesurfaces in parallel.

System 100 may include a head-disk assembly (HDA) 102 that may includetwo magnetic storage mediums 104 and 106. The HDA 102 may furtherinclude read/write heads 108 and 110 which may read and write to the topand bottom magnetic storage surfaces of the magnetic storage medium 104,respectively, and read/write heads 112 and 114 which may read and writeto the top and bottom magnetic storage surfaces of the magnetic storagemedium 106, respectively. As shown with regard to the read/write heads108, each surface may have a read head (e.g. read head 108(1)) and awrite head (e.g. write head 108(2)). The read head and write head of asurface may be separated by a non-negligible distance (e.g., 100tracks). Though not shown, each of read/write heads 110-114 may alsoinclude a read head and a write head. Each of the read/write heads mayinclude multiple read-sensors (or readers) fabricated on a singleread-head such that multiple copies of a read-back signal may beobtained simultaneously from the respective magnetic storage surface(e.g. from a particular track) and a writer fabricated on a write-headto be utilized for data storage to the respective magnetic storagesurface. Each of the read/write heads 108-114 may be mounted on aslider, all of which may connect to an actuator arm for positioning overthe media. A servo control may be configured to drive a servo mechanismwhich may move the slider to position the read/write heads in a desiredlocation relative to the magnetic storage surfaces of the magneticstorage mediums 104 and 106.

In addition, the system 100 may include micro head actuators that mayallow for read/write head locations to deviate, by a small amount, fromtheir location at the end of the slider arm. In some embodiments, themicro head actuators may be independently controlled from one another.This may allow for multiple heads to be positioned over respective trackcenters even when the track centers are not exactly aligned to theslider location. For example, micro head actuators may allow for thereaders, writer, or both of 108 to be centered over a track on the topmagnetic storage surface of the magnetic storage medium 104 while thereaders, writer, or both of 114 are centered over a track on the bottommagnetic storage surface of the magnetic storage medium 106, even thoughthe tracks are not exactly aligned with one another. In another example,micro head actuators may allow for the readers, writer, or both of 108to be centered over a track on the top magnetic storage surface of themagnetic storage medium 104 while the readers, writer, or both of 110are centered over a track on the bottom magnetic storage surface of themagnetic storage medium 104, even though the tracks are not exactlyaligned with one another.

Referring to FIG. 2, a diagram of a surface of an example magneticstorage medium (e.g. 104 and 106) of the multi-sensor magnetic recording(MSMR) system architecture 100 is shown and is generally designated 200.More particularly, surface 200 may generally show the layout of positioninformation such as servo or RRO/ZAP fields on a surface of a magneticstorage medium of a hard disk drive.

The position information may allow the hard drive to determine theposition of a read/write heads relative to the surface of the magneticstorage medium. The examples herein include parallelized writing RRO/ZAPfields based on servo information. This is merely done as an example andembodiments are not so limited and other position information schemesmay be utilized.

Reliable storage of data, and its subsequent retrieval, from a hard diskdrive (HDD) may require that the read/write heads be placed over thespinning media with a very high degree of accuracy. To achieve this, aservo pattern (or other position information) may be written to themedia during manufacturing which may contain information regardingradial and tangential positioning on the disk. As shown in FIG. 2, theservo pattern may span from the inner diameter 202 of the disk to theouter diameter of the disk 204 and may be placed at regular intervalsaround the disk. As shown, the servo wedges 206 may be separated by dataregions 208 that may store non-servo data (e.g. user data). The servopattern may be demodulated each time a read-head passes over a servosector 210 in the servo wedges 208. The demodulated information may thenbe used to determine a location of the read-head from which thewrite/head position may be inferred. Based on the determined location ofthe read/write head, deviations from the desired position may bedetermined and rectified to maintain the integrity of the operation(e.g. read/write/seek/etc.).

As mentioned above, writing the servo pattern to the disk may beaccomplished at the time of manufacturing using either a dedicatedmachine (known as a servo disk writer (SDW) or a multi-disk writer(MDW)) or through a process known as self-servo write (SSW), in whichthe embedded controller may be used to write servo pattern. Although theservo pattern may be directly used for the servo operation, its use maybe complicated by written-in eccentricities in the servo pattern, aphenomenon depicted in FIG. 2. As shown, a servo track 212 may bedefined as a set of servo sectors 210 written at an (approximately)equal radius from the disk center (e.g. servo sectors sharing a trackid, which may be written into the servo sectors). Due to imperfectionsin the servo writing procedure, not all servo sectors may fall on theidealized, circular, track shown as the dashed line of the servo track212 in FIG. 2 (offset servo sector 214). As such, an attempt to followthe written servo track 212 may entail moving the read-head continuallyinwards and outwards to match the trajectory of the irregularly shapedtrack 212. This phenomenon, known as repeatable runout (RRO), may causeperformance degradation and may limit the achievable linear trackdensity of an HDD.

In some examples, RRO, which may generally be characterized as anon-zero mean of the generated radial position error associated with agiven servo sector 210, may be compensated. For this, after the servopattern is written, the system may learn the eccentricity by following agiven servo track 212 and monitoring a repeatable portion. The learnedvalues may be used to generate compensation factors that may then bewritten as fields following each servo sector 210 such that thecompensation factors may be retrieved and used during normal operationof the servo system. These fields may be referred to as either RROfields or Zero Acceleration Profile (ZAP) fields.

The process of writing ZAP fields may be time consuming. Although thetime to compute the compensation values may be reduced by onlyconsidering a subset of tracks and using interpolation to determine thevalues in-between, the writing process may be conducted for every servosector 210 on the magnetic storage surface 200. As an elongatedmanufacturing time may directly correspond to an increase in cost,reducing manufacturing time may be desirable. Some embodiments hereinmay allow for the parallelization of ZAP field writes. However, asmentioned above, embodiments are not limited to writing ZAP fields orservo information. Rather, embodiments may be applied to parallelizedwriting of any information to multiple disk surfaces. Further, in someembodiments, the architecture disclosed herein may require minimalchanges from a MSMR architecture.

As mentioned above, the systems and techniques disclosed herein mayallow for the parallelized writing of ZAP fields to a plurality ofstorage surfaces, which may save significant manufacturing time that isotherwise consumed with this activity.

Returning to FIG. 1, the disclosed HDA 102 and multi-sensor magneticrecording (MSMR) system architecture 100 may include coupling of thereaders of the read/write heads 108-114 to the input paths that includethe analog front-ends (AFEs) 116 and 118 (e.g. illustrated as the inputsto 116 and 118) which in turn may be coupled to respective servochannels 120 and 122. The system may further include phase locked loops(PLLs) 124 and 126. The servo channels 120 and 122 and PLLs 124 and 126may be coupled to MUXs 128-132. In turn, the MUXs 124 and 128 may becoupled to the serialize circuit 134. The outputs of the MUX 130 and theserialize circuit 134 may be coupled to an output or write path that mayinclude the writers of the read/write heads 108-114. In addition, thesystem may further include a controller 162 coupled to the MUXs 128-130.

Each of the HDA 102, the AFEs 116 and 118, the servo channels 120 and122, PLLs 124 and 126, the MUXs 128-132, the serialize circuit 134 andcontroller 162 may be a separate circuit, a system on chip (SOC),firmware, a processor(s), or other system not listed, or any combinationthereof.

As mentioned above, the read/write heads 108 and 110 (e.g. the readersor read-sensors thereof) may read from respective magnetic storagesurfaces of the magnetic storage mediums 104 and 106. The readers of theread/write heads 108 and 110 may each produce a continuous time inputsignal from magnetic interactions with the respective surfaces. Thereaders may be selectively coupled to the AFEs 116 and 118 such thatcontinuous time input signals from selected readers may be provided tothe AFEs 116 and 118 as continuous time input signals r₀(t) 136 andr₁(t) 138. The AFEs 116 and 118 may process r₀(t) 136 and r₁(t) 138 toproduce filtered and gain-adjusted continuous time input signals whichmay in turn be provided to the servo channels 120 and 122 respectively.For example, in operation, the AFEs may each receive a continuous-timesignal and perform processing such as analog filtering and applying again.

The PLLs 124 and 126 may each operate to produce a clock signal c₀ 152and c₁ 154 which may then be provided to the MUX 132 and a respectivepair of the AFE 116 and servo channel 120 or AFE 118 and servo channel122.

The servo channels 120 and 122 may produce respective disk locked clocksignals dlc₀ 140 and dlc₁ 142 and provide dlc₀ 140 and dlc₁ 142 to PLLs124 and 126, respectively, as feedback. The disk locked clock signalsmay allow for the frequency and phase of the sampling clocks produced bythe PLLs for the AFEs to be locked to the servo pattern written to therespective magnetic storage surface (or to be written to the respectivemagnetic storage surface). By providing respective PLLs for each AFE andservo channel (e.g. for each surface being written), the clock domainsand one or both of the frequency and the phase used for each surface maybe independent. For example, the PLLs may receive the disk locked clocksignals dlc₀ 140 and dlc₁ 142 and adjust the frequency and phase used togenerate the clock signals c₀ 152 and c₁ 154.

In addition, the servo channels 120 and 122 may process the continuoustime signals processed by the AFE 116 and 118, respectively. Dependingon what data is to be written to the magnetic storage surfaces, theprocessing may differ. In an example in which RRO/ZAP fields are to bewritten, the servo channels 120 and 122 may detect already written servoinformation and output a RRO/ZAP field data as wdo₀ 144 and wdo₁ 146 anda write gate signal as wg₀ 148 and wg₁ 150, respectively, to cause arespective writer to write the RRO/ZAP field data to the respectivemagnetic storage surface. In other examples in which servo fields are tobe written, similar operations may be performed by the servo channels120 and 122 with regard to pre-servo field markings (e.g. spiralpatterns).

As mentioned before, the architecture illustrated in FIG. 1 may be anexample embodiment which has few changes from an MSMR architecture. Forexample, an MSMR architecture includes multiple read paths for themultiple readers on each read head (e.g. reading a same track) butincludes one write path for the single writer on each MSMR write head.Similarly, in the architecture of FIG. 1, the write path has not beenduplicated. It should be noted that embodiments according to thisdisclosure are not so limited and may include architectures performingsimilar functions with any number of write paths.

In the case of architectures similar to FIG. 1, the non-duplication ofthe write path may result in corruption of servo or RRO/ZAP fields whenthe servo fields are aligned or closely spaced in the direction ofrotation of the HDA. For example, when the RRO fields are aligned, bothservo channels may attempt to write over the single path simultaneously,resulting in corruption of one or more of the fields. As such, MSMRsystems according to this disclosure may be configured to perform writeaccess control and error recovery between the servo channels such thatthe writers may be prevented from attempting to write simultaneouslywhich may otherwise cause corruption of the servo or position markings.

To provide such write control, the system 100 may include the MUXs128-132 that may select between the servo channels based on the selectsignal 156 which may be provided by a firmware or hardware controller162. In particular, the MUX 128 may receive the write data wdo₀ 144 andwdo₁ 146 from the servo channels 120 and 122 and select between wdo₀ 144and wdo₁ 146 based on the select signal 156. The MUX 130 may receive thewrite gate signals wg₀ 148 and wg₁ 150 from the servo channels 120 and122 and select between wg₀ 148 and wg₁ 150 based on the select signal156. MUX 130 may output the selected write gate wg₀ 148 or wg₁ 150 as wg160. In addition, the MUX 132 may receive the clock signals c₀ 152 andc₁ 154 from the PLLs 124 and 126 and select between c₀ 152 and c₁ 154based on the select signal 156. In some embodiments, the separationbetween servo wedges on different surfaces in the direction of rotationmay be sufficient to allow a firmware controller of a MSMR hard drive tocontrol the selection of the servo channel 120 or 122 which is allowedto write. In such examples, the controller 162 may alternate writeaccess between a plurality of servo channels based on a predeterminedpattern or based on a pattern determined by the controller 162 duringthe determination of the RRO. In other examples, such as that shown inFIG. 3 and described below, feedback may be included between the servochannels and a hardware or firmware controller which may allow for arequesting of write access, assignment of write access, and for theservo channel with write access to inform the hardware or firmwarecontroller of the completion of writing. The feedback system may alsoallow the controller to deny write access when another servo channel hasalready been assigned and has not relinquished write access.

The serialize circuit 134 may operate to receive one of the write datawdo₀ 144 or wdo₁ 146 from the MUX 128 (e.g. based on the select signal156) and output the continuous-time write waveform wdo 158 to a writepath and writer corresponding to the reader whose input signal is beingprocessed by the servo channel with write access. As shown in FIG. 1,the logic of the serialize circuit 134 may change between being clockedby the PLL 124 and PLL 126 based on the select signal 156. In thismanner, the output frequency may be matched to the input frequency.

FIG. 3 illustrates a block diagram of a multi-sensor magnetic recording(MSMR) system architecture which may include functionality to writeposition information such as servo fields, RRO/ZAP fields or otherformatting information to a plurality of storage surfaces in parallel isshown and is generally designated 300. More particularly, FIG. 3 mayillustrate an example embodiment of a MSMR hard drive similar to thatshown in FIG. 1 which includes a hardware write control module WCM 302.In some examples, the use of a write control module WCM 302 may allowfor the servo wedges or RRO/ZAP fields being written to be closer thanmay be possible using firmware.

As the operation of items 102-118 and 124-134 in FIG. 3 is similar tothat discussed in FIG. 1, these operations will not be fully discussedagain with regard to FIG. 3. In summary, the analog front-ends (AFE 116and AFE 118) may receive respective read-back signals r₀(t) 136 andr₁(t) 138. Each signal 136 and 138 may come from a different surface(which can be different surfaces of the same disk or from differentdisks). In particular, these read-back signals may come from thesurfaces on which a parallelized write of ZAP fields is being performed.

As with FIG. 1, the system 300 may utilize the multiple read paths andsingle write path of a MSMR architecture. However, instead of readingusing the multiple heads disposed above each surface, system 300 maydirect the read signal from a single head for each surface being writtenover a respective one of the multiple read paths. In some examples, thesystem 300 may use micro head actuator technology to enable eachread/write head to follow a respective servo track of a respectivesurface in an independent manner. This may allow the RRO to beeffectively learned and the respective write-heads to be positioned atthe respective desired locations.

The multiple read signals may be processed by respective AFEs 116 and118 and then respective servo channels 304 and 306. Aside from thedifferences discussed below, the operation of the servo channels 304 and306 may be similar to those of servo channels 120 and 122 discussedabove. As with FIG. 1, the servo channels 304 and 306 may operate ondifferent clock domains. More particularly, the operation of the disklocked clock signals dlc₀ 140 and dlc₁ 142 may lock each PLL 124 and 126to the written servo pattern it is demodulating (e.g. of read-backsignals r₀(t) 136 and r₁(t) 138, respectively).

As discussed above, the independent operation of the servo channels mayallow each to be locked to its respective surface such that either mayinitiate a ZAP write to the disk. Because the system 300 may include asingle wdo port (e.g. write path), the servo channels 304 and 306 maycommunicate with the WCM circuit 302 to handle the sharing of the wdoline between the servo channels. It should be noted that embodiments arenot limited to a single wdo port or write path and other embodiments mayinclude any number of write paths.

In operation, each servo channel 304 and 306 may process the signal fromits AFE 116 and 118 to determine the RRO/ZAP field write location. Atthe appropriate time prior to the determined write location, a servochannel may generate a write-data output pattern wdo₀ 144 or wdo₁ 146,may request write access from the WCM 302 along line w 308 or 310 andmay output a write gate signal wg₀ 148 or wg₁ 150 to the MUX 130.

The write control module (WCM) 302 may receive the write access requestalong line w 308 or 310. The WCM 302 may determine whether write accesshas already been granted to another servo channel. If write access hasalready been granted to another servo channel, the WCM 302 may denywrite access to the requesting servo channel 304 or 306 using therespective access control line (e.g. acc 312 or 314) and may generate anerror. On the other hand, if write access has not already been granted,the WCM 302 may provide write access to the requesting servo channel 304or 306 along the respective access control line (e.g. acc 312 or 314)and update its state to indicate write access is currently being used bythe requesting servo channel. The WCM 302 may further generate or updatea select signal 316 and output the select signal 316 to the MUXs 128-132such that the MUXs 128-132 select inputs associated with the requestingservo channel. Upon receiving write access, the servo channel 304 or 306may output the write data via the serialize circuit 134. Once the servochannel completes the write operation, the servo channel may inform theWCM 302 using w 308 or 310 to relinquish control such that it may begranted to another servo channel.

As mentioned above, if a write access error occurs (e.g. due to a servochannel requesting write access while another servo channel is writing),an error handling process may be initiated. The error handling processmay vary between embodiments. In some embodiments, the location of theRRO/ZAP field which was not written due to the denied write request maybe stored, a counter may be incremented, and the process may continuefor a current revolution. At the end of a current revolution, writes maybe performed for the RRO/ZAP fields which were not written due to deniedwrite requests. In addition, the counter may be checked to determinewhether a threshold number of errors occurred. If the threshold numberof errors occurred, various changes may be made to the write process.For example, the parallel RRO/ZAP writing process may be discontinuedfor the current surfaces or for one or more surfaces which haveconflicting write times (e.g. where two out of three surfaces areconflicting, writing to one of the conflicting surfaces may bediscontinued until writing has completed for the remaining twosurfaces). In another example, if a surface not involved in the currentwriting process remains for RRO/ZAP fields writing, one of theconflicting surface may be discontinued while the uninvolved surface iswritten with the remaining conflicting surface(s). These are merelyexamples of error handling processes and, in view of this disclosure,one of ordinary skill in the art would envision may additionalvariations.

Although this disclosure provided examples of parallelizing RRO/ZAPfield writes to two storage surfaces, the systems and processesdisclosed herein may be generalized to an arbitrary number ofparallelized writes. For example, some embodiments may provideparallelization beyond the number of readers by adding additionalread-signal input ports and servo channels. One of ordinary skill in theart would envision may additional variations in view of this disclosure.

Referring to FIG. 4, a flowchart of a method that may controlparallelized writing of RRO/ZAP fields to multiple storage surfaces isshown and is generally designated 400. More particularly, flowchart 400may be a flow of operations of the systems 100-300 detailed above withrespect to FIGS. 1-3.

In operation, the system may read servo information from a plurality ofsurfaces and determine the repeatable run out (RRO) for regions of eachof a plurality of surfaces at 402. At 404, the system may initialize theparallelized writing of RRO/ZAP fields in which the servo channelsreceive and process read data, trigger write gates and request writecontrol upon determining RRO/ZAP fields are to be written to respectivesurfaces, write data when given write access and return control whenRRO/ZAP fields are written. At 406, the write control module (e.g.firmware, WCM 302, etc.) may determine whether an event has occurred. At408, the write control module may determine what type of an event hasoccurred and continues to one of 410, 412 or 414 based on thedetermination (e.g. to 410 if a write request is received while writecontrol is already assigned to another servo channel, to 412 if a writerequest is received while write control is free or to 414 if a releaseof write control is received). At 410, if the event is a write requestand the write control module determines that write access has alreadybeen granted to another servo channel, the write control module mayblock the write access request and inform an error handling system. Theerror handling system may operate in a manner similar to that discussedabove. At 412, if the event is a write request and the write controlmodule determines that write access is available to be granted to therequesting servo channel, the write control module may pass writecontrol the requesting to servo channel and set a register to causeother servo channel write access requests to be blocked. At 414, if arelease of write control is received from a servo channel, the registermay be cleared to allow for a servo channel to request write access.

All steps listed for the method 400 may be applied to multiple inputsystems. Many variations would be apparent in view of this disclosure.Further, though FIGS. 3 and 4 discuss examples involving theparallelized writing of RRO/ZAP fields, embodiments are not so limitedand other embodiments may utilize the same techniques to performparallelized writing of other position information. Components andcircuits used to perform the operations in the method may be discrete,integrated into a system on chip (SOC), or other circuits. Further, thesteps can be carried out in a processor (e.g. a digital signalprocessor), implemented in software, implemented via firmware, or byother means.

Referring to FIG. 5, a block diagram of a system including amulti-sensor magnetic recording (MSMR) system architecture which mayinclude functionality to write position information such as servofields, RRO/ZAP fields or other formatting information to a plurality ofstorage surfaces in parallel is shown and generally designated 500. Thesystem 500 can be an example of a data storage device (DSD), and may bean example implementation of system 100. The DSD 516 can optionallyconnect to and be removable from a host device 514, which can be adevice or system having stored data, such as a desktop computer, alaptop computer, a server, a digital video recorder, a photocopier, atelephone, a music player, other electronic devices or systems notlisted, or any combination thereof. The data storage device 516 cancommunicate with the host device 514 via the hardware/firmware basedhost interface circuit 512 that may include a connector (not shown) thatallows the DSD 516 to be physically connected and disconnected from thehost 514.

The DSD 516 can include a system processor 502, which may be aprogrammable controller, and associated memory 504. The system processor502 may be part of a system on chip (SOC). A buffer 506 may temporarilystore data during read and write operations and can include a commandqueue. The read/write (R/W) channel 510 can encode data during writeoperations to, and reconstruct data during read operations from, thedata storage medium 508. The data storage medium 508 is shown anddescribed as a hard disc drive, but may be other types of magneticmedium, such as a flash medium, optical medium, or other medium, or anycombination thereof.

The R/W channel 510 may receive data from more than one data storagemedium at a time, and in some embodiments can also receive multiple datasignals concurrently, such as from more than one output of a reader.Multi-sensor magnetic recording (MSMR) systems can receive two or moreinputs from multiple sources (e.g. recording heads, flash memory,optical memory, and so forth) associated with the same magnetic medium.The R/W channel 510 can combine multiple inputs and provide a singleoutput, as described in examples herein.

The block 518 can implement all of or part of the systems andfunctionality of systems and methods 100-400. In some embodiments, theblock 518 may be a separate circuit, integrated into the R/W channel510, included in a system on chip, firmware, software, or anycombination thereof.

In the examples discussed herein, two signals are received andprocessed. However, the systems and methods discussed herein may begeneralized to any number (N) of signals. Many variations would beapparent to one of ordinary skill in the art in view of this disclosure.

The illustrations, examples, and embodiments described herein areintended to provide a general understanding of the structure of variousembodiments. The illustrations are not intended to serve as a completedescription of all of the elements and features of apparatus and systemsthat utilize the structures or methods described herein. Many otherembodiments may be apparent to those of skill in the art upon reviewingthe disclosure. Other embodiments may be utilized and derived from thedisclosure, such that structural and logical substitutions and changesmay be made without departing from the scope of the disclosure. Forexample, the figures and above description provide examples ofarchitecture that may be varied, such as for design requirements of asystem. Moreover, although specific embodiments have been illustratedand described herein, it should be appreciated that any subsequentarrangement designed to achieve the same or similar purpose may besubstituted for the specific embodiments shown.

This disclosure is intended to cover any and all subsequent adaptationsor variations of various embodiments. Combinations of the aboveexamples, and other embodiments not specifically described herein, willbe apparent to those of skill in the art upon reviewing the description.Additionally, the illustrations are merely representational and may notbe drawn to scale. Certain proportions within the illustrations may beexaggerated, while other proportions may be reduced. Accordingly, thedisclosure and the figures are to be regarded as illustrative and notrestrictive.

What is claimed is:
 1. An apparatus comprising: a first servo channelconfigured to output first position information to a first writer via ashared write path such that the first writer writes the first positioninformation to a first magnetic recording medium surface; a second servochannel configured to output second position information to a secondwriter via the shared write path such that the second writer writes thesecond position information to a second magnetic recording mediumsurface; a controller configured to control the shared write path suchthat write access is changed between the first servo channel and secondservo channel a plurality of times during a revolution of the firstmagnetic recording medium surface and second magnetic recording mediumsurface.
 2. The apparatus of claim 1, further comprising the firstwriter configured to write to the first magnetic recording mediumsurface; the second writer configured to write to the second magneticrecording medium surface; a first reader configured to read from thefirst magnetic recording medium surface to generate a first read signal;the first servo channel configured to determine a first write positionat which to write the first position information based at least in parton the first read signal; a second reader configured to read from thesecond magnetic recording medium surface to generate a second readsignal; and the second servo channel configured to determine a secondwrite position at which to write the second position information basedat least in part on the second read signal.
 3. The apparatus of claim 2,further comprising the first reader and the second reader being readersof a multi-sensor magnetic recording (MSMR) hard drive.
 4. The apparatusof claim 2, further comprising the first servo channel being configuredto request write access from the controller based on the determinedfirst write position.
 5. The apparatus of claim 4, further comprisingthe controller being configured to: receive the request for write accessfrom the first servo channel; determine that write access is available;and assign write access to the first servo channel.
 6. The apparatus ofclaim 5, further comprising the first servo channel being furtherconfigured to: receive the assignment of write access; output the firstposition information to the first writer via the shared write path; andreturn write access to the controller when the output of the firstposition information is complete.
 7. The apparatus of claim 4, furthercomprising the controller being configured to: receive the request forwrite access from the first servo channel; determine that write accessis not available; and deny write access to the first servo channel. 8.The apparatus of claim 7, further comprising: a first phase locked loop(PLL) configured to output a first clock signal to the first servochannel and shared write path; the first servo channel furtherconfigured to generate a first disk locked clock signal to the first PLLto lock the first clock signal to the data stored on the first magneticrecording medium surface; a second PLL configured to output a secondclock signal to the second servo channel and shared write path; thesecond servo channel further configured to generate a second disk lockedclock signal to the second PLL to lock the second clock signal to thedata stored on the second magnetic recording medium surface; and thecontroller configured to control the shared write path to operate basedon one of the first clock signal and second clock signal based onassignment of write access to a respective one of the first servochannel and the second servo channel.
 9. The apparatus of claim 7,further comprising the first position information and the secondposition information being RRO/ZAP information.
 10. A system comprising:a first servo channel configured to output first position information toa first writer such that the first writer writes the first positioninformation to a first magnetic recording medium surface of a hard diskdrive; a second servo channel configured to output second positioninformation to a second writer such that the second writer writes thesecond position information to a second magnetic recording mediumsurface of the hard disk drive, the first servo channel including afirst circuit and the second servo channel including a second circuitseparate from the first circuit; the first servo channel configured tooutput the first position information to the first writer such that thefirst position information is written to a first location and a secondlocation, separate from the first location, during a particularrevolution; and the second servo channel configured to output the secondposition information to the second writer such that the second positioninformation is written to a third location during the particularrevolution, the third location between the first location and secondlocation.
 11. The system of claim 10 further comprising: the firstwriter configured to write to the first magnetic recording mediumsurface of the hard disk drive; the second writer configured to write tothe second magnetic recording medium surface of the hard disk drive; thefirst servo channel being configured to output the first positioninformation to the first writer via a shared write path; the secondservo channel being configured to output the second position informationto the second writer via the shared write path; a controller configuredto control the shared write path such that write access is changedbetween the first servo channel and second servo channel a plurality oftimes during a revolution of the first magnetic recording medium surfaceand second magnetic recording medium surface.
 12. The system of claim 11further comprising: a first reader configured to read from the firstmagnetic recording medium surface to generate a first read signal; thefirst servo channel configured to determine a first write position atwhich to write the first position information based at least in part onthe first read signal; a second reader configured to read from thesecond magnetic recording medium surface to generate a second inputsignal; and the second servo channel configured to determine a secondwrite position at which to write the second position information basedat least in part on the second read signal.
 13. The system of claim 12further comprising the first servo channel being configured to requestwrite access from the controller based on the determined first writeposition.
 14. The system of claim 13 further comprising the controllerbeing configured to: receive the request for write access from the firstservo channel; determine that write access is available; and assignwrite access to the first servo channel.
 15. The system of claim 14further comprising: further comprising the first servo channel beingfurther configured to: receive the assignment of write access; outputthe first position information to the first writer via a shared writepath; and return write access to the controller when the output of thefirst position information is complete.
 16. The system of claim 14further comprising: a first phase locked loop (PLL) configured to outputa first clock signal to the first servo channel and shared write path;the first servo channel further configured to generate a first disklocked clock signal to the first PLL to lock the first clock signal tothe data stored on the first magnetic recording medium surface; a secondPLL configured to output a second clock signal to the second servochannel and shared write path; the second servo channel furtherconfigured to generate a second disk locked clock signal to the secondPLL to lock the second clock signal to the data stored on the secondmagnetic recording medium surface; and the controller configured tocontrol the shared write path to operate based on one of the first clocksignal and second clock signal based on assignment of write access to arespective one of the first servo channel and the second servo channel.17. The system of claim 12 further comprising the first reader and thesecond reader being readers of a multi-sensor magnetic recording (MSMR)hard drive.
 18. A method comprising: during a revolution of a hard diskassembly of a multi-sensor magnetic recording (MSMR) hard drive:reading, by a first reader of the MSMR hard drive, from a first magneticrecording medium surface to generate a first read signal; determining,by a first servo channel of the MSMR hard drive, a first write positionat which to write first position information based at least in part onthe first read signal; requesting, from a controller of the MSMR harddrive, by the first servo channel, write access to a shared write pathbased on the determined first write position; receiving, by the firstservo channel, a first assignment of write access; outputting, by thefirst servo channel, the first position information to a first writervia the shared write path; and returning, by the first servo channel,write access to the controller when the output of the first positioninformation is complete; reading, by a second reader of the MSMR harddrive, from a second magnetic recording medium surface to generate asecond read signal; determining, by a second servo channel of the MSMRhard drive, a second write position at which to write second positioninformation based at least in part on the second read signal;requesting, from the controller of the MSMR hard drive, by the secondservo channel, write access to the shared write path based on thedetermined second write position; receiving, by the second servochannel, a second assignment of write access; outputting, by the secondservo channel, the second position information to a second writer viathe shared write path; and returning, by the second servo channel, writeaccess to the controller when the output of the second positioninformation is complete.
 19. The method of claim 18 further comprisingreceiving, by the controller, the request for write access from thefirst servo channel; determining, by the controller, that write accessis available; and assigning, by the controller, write access to thefirst servo channel and sending the first assignment of write access tothe first servo channel.
 20. The method of claim 18 further comprising:determining, by the first servo channel of the MSMR hard drive, a thirdwrite position at which to write third position information based atleast in part on the first read signal; requesting, from a controller ofthe MSMR hard drive, by the first servo channel, write access to theshared write path based on the determined third write position;receiving, by the first servo channel, a third assignment of writeaccess; outputting, by the first servo channel, the first positioninformation to the first writer via the shared write path; andreturning, by the first servo channel, write access to the controllerwhen the output of the first position information is complete.